linux-kernel - Re: Question: livepatch failed for new fork() task stack unreliable

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Date:   Tue, 30 Jun 2020 16:36:39 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     "Wangshaobo (bobo)" <bobo.shaobowang@...wei.com>
Cc:     huawei.libin@...wei.com, xiexiuqi@...wei.com,
        cj.chengjian@...wei.com, mingo@...hat.com, x86@...nel.org,
        linux-kernel@...r.kernel.org, live-patching@...r.kernel.org,
        mbenes@...e.cz, devel@...ukata.com, viro@...iv.linux.org.uk,
        esyr@...hat.com
Subject: Re: Question: livepatch failed for new fork() task stack unreliable

On Tue, Jun 30, 2020 at 09:04:12PM +0800, Wangshaobo (bobo) wrote:
> 
> 在 2020/6/5 9:51, Josh Poimboeuf 写道:
> > On Fri, Jun 05, 2020 at 09:26:42AM +0800, Wangshaobo (bobo) wrote:
> > > > > So, I want to ask is there any side effects if i modify like this ? this
> > > > > modification is based on
> > > > > 
> > > > > your fix. It looks like ok with proper test.
> > > > > 
> > > > > diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c
> > > > > index e9cc182aa97e..ecce5051e8fd 100644
> > > > > --- a/arch/x86/kernel/unwind_orc.c
> > > > > +++ b/arch/x86/kernel/unwind_orc.c
> > > > > @@ -620,6 +620,7 @@ void __unwind_start(struct unwind_state *state, struct
> > > > > task_struct *task,
> > > > >                   state->sp = task->thread.sp;
> > > > >                   state->bp = READ_ONCE_NOCHECK(frame->bp);
> > > > >                   state->ip = READ_ONCE_NOCHECK(frame->ret_addr);
> > > > > +              state->signal = ((void *)state->ip == ret_from_fork);
> > > > >           }
> > > > > 
> > > > > diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c
> > > > > index 7f969b2d240f..d7396431261a 100644
> > > > > --- a/arch/x86/kernel/unwind_orc.c
> > > > > +++ b/arch/x86/kernel/unwind_orc.c
> > > > > @@ -540,7 +540,7 @@ bool unwind_next_frame(struct unwind_state *state)
> > > > >            state->sp = sp;
> > > > >            state->regs = NULL;
> > > > >            state->prev_regs = NULL;
> > > > > -        state->signal = ((void *)state->ip == ret_from_fork);
> > > > > +        state->signal = false;
> > > > >            break;
> > > > Yes that's correct.
> > > Hi, josh
> > > 
> > > Could i ask when are you free to send the patch, all the tests are passed
> > > by.
> > I want to run some regression tests, so it will probably be next week.

Sorry, I was away for a bit and I didn't get a chance to send the patch.
I should hopefully have it ready soon.

-- 
Josh